During the last decade, an increasing interest has been developed in the art of perfumery for materials possessing a woody-type odour. One of the consequences of such an increase of interest consisted to promote a drastic shortage of naturally occurring materials traditionally used in the art for the reconstitution of woody-type olfactive notes.
Patchouli oil is an example of this type of material. This essential oil is well known in the art for its typical woody and balsamic fragrance, at the same time spicy, sweet and herbaceous. The said essential oil is moreover noteworthy for its particularly tenacious and powerful odour, and consequently is very broadly used in perfumery, particularly in fine perfumery, for the preparation of various compositions such as those having an oriental, woody, "chypre" or "fougere" character for example.
It has been surprisingly found that it is now possible to faithfully reproduce certain typical nuances of the odoriferous character of natural patchouli oil, by using spirane derivatives of formula (II).
2,6,10,10-Tetramethyl-1-oxa-spiro[4.5]decan-6-ol for example, when used in a perfume or in a perfumed product, imparts thereto an elegant and harmonious woody and balsamic olfactive note similar to that obtained by the use of patchouli oil itself.
It is known in the art that the fragrance of a given essential oil results from the combination of the different odours of each individual constituent of the said oil and can vary depending on the origin or on the purity of the said natural essential oil. It is therefore very rare to find that a single compound can by itself totally reproduce the full character of an essential oil.
In certain cases however, patchouli oil can be advantageously replaced by the spiranic compounds (II) whenever it is desired to impart to a perfume or a perfumed product the woody and balsamic note typical of the said essential oil.
PREFERRED EMBODIMENTS OF THE INVENTION
We have surprisingly found that the compounds of formula (II) are characterized by their woody-type odour. Ester derivatives of formula (II) differ from the corresponding alcohols by a greater diffuseness associated with an amber-like, balsamic, flowery and even herbaceous note.
Spirane derivatives (II) are particularly useful in fine perfumery as well as for the preparation of perfumed products such as soaps, detergents, household materials or cosmetic preparations for example. The compounds of formula (II), particularly 2,6,9,10,10-pentamethyl-1-oxa-spiro[4.5]decan-6-yl acetate, can also develop fruity sulfury organoleptic notes which are reminiscent of the character developed by blackcurrent fruits.
When compounds (II) are used as ingredients for the preparation of perfume compositions, the proportions used may vary within a wide range and are generally comprised between about 1 and 10% (parts by weight) of the said composition. Higher proportions, in some instances up to 50 or even 80%, can also be used when compounds (II) are used as reinforcing agents in base perfume compositions. Lower proportions of the order of about 0.01% to 0.1% are used whenever the compounds of formula (II) are employed to perfume products as soaps or detergents.
Owing to their particular organoleptic properties, compounds (II) can also be used in the flavour industry as ingredients for the preparation of artificial flavours or for the aromatization of foodstuffs, animal feeds, beverages, pharmaceutical preparations and tobacco products.
Depending on the nature of the products in which they are incorporated, compounds (II) can enhance or develop various gustative notes such as woody, amber-like, earthy and in certain cases slightly flowery notes, or even notes reminiscent of that of cedar wood oil. Compounds (II) are therefore particularly appreciated for the preparation of artificial flavours such as citrus fruits or even mushroom flavours wherein the woody and earthy gustative note is often requested.
Compounds (II) can also advantageously be used for flavouring tobacco or tobacco products by imparting thereto a woody, amber-like and cedar wood-like note reminiscent of that of oriental tobaccos.
The woody and earthy note typical of certain compounds (II) is also appreciated for the aromatization of infusions or decoctions such as tea, camomile or verbena for example.
The term "foodstuff" is here used broadly and includes also products such as coffee, tea or chocolate.
Depending on the nature of the flavoured material or on the organoleptic effects desired, the proportions used may vary within a wide range. When compounds (II) are used as ingredients for flavouring foodstuffs or beverages for example, interesting effects may be achieved by the use of proportions comprised between about 0.01 and 20 ppm, based on the weight of the flavoured material. For the aromatization of tobacco or tobacco products the proportions used are often comprised between 0.5 and 500 ppm, preferably between 30 and 50 ppm.
When compounds (II) are used for the preparation of artificial flavours, they are generally used in proportions up to 20%, or even more, of the weight of the said composition.
In all cases, depending on the olfactive or gustative effects desired, smaller or higher proportions than those given above can also be used.
Most of the spirane derivatives of formula (II) which can be used in accordance with the present invention are novel compounds, these latter ones being represented by general formula (I).
In contradistinction, 2,6,10,10-tetramethyl-1-oxa-spiro[4.5]decan-6-ol is a prior known compound, the preparation thereof being described in Tetrahedron Letters 1969, 1955. It has to be noted however that the above reference does not mention any organoleptic properties of said alcohol nor does it suggest its use as perfuming or flavouring ingredient.
Also new are the following spirane derivatives: 2,6,10,10-tetramethyl-1oxa-spiro[4.5]dec-3-en-6-ol, 6,7-epoxy-2, 6,10,10-tetramethyl-1-oxa-spiro[4.5]decane, 2,6,9,10,10-pentamethyl-1-oxa-spiro[4.5]deca-3,6-diene, 2,6,9,10,10-pentamethyl-6,7-epoxy-1-oxa-spiro[4.5]dec-3-ene and 2,6,9,10,10-pentamethyl-6,7-epoxy-1-oxa-spiro[4.5]decane, useful as intermediate compounds in the preparation of spirane derivatives (II), in accordance with one of the objects of the present invention. The first two of the above mentioned compound may be used, in a one step process, as starting material for preparing 2,6,10,10-tetramethyl-1-oxa-spiro[4.5]decan-6-ol [R.sup.1 =H in formula (II)] as following:
2,6,10,10-tetramethyl-1-oxa-spiro[4.5]dec-3-en-6-ol can be converted into the desired alcohol by means of a catalytic haydrogenation; and PA1 6,7-epoxy-2,6,10,10-tetramethyl-1-oxa-spiro[4.5]decane can be reduced by means of lithiumaluminium hydride to give the desired alcohol. PA1 (a) directly mixing the diol (III) with the alkali metal hydrogenosulfate and subsequently heating the thus obtained mixture at a temperature comprised between about 50.degree. and 150.degree. C. preferably under reduced pressure, or PA1 (b) dissolving compound (III) in an inert organic solvent such as an aromatic hydrocarbon, toluene or benzene e.g., or a halogenated hydrocarbon, methylene chloride or chloroform e.g., and subsequently heating the above solution at the boiling temperature, in the presence of alkali metal hydrogenosulfate.
Due to the presence of several chirality centres in the molecule, namely at carbon atoms 2, 5 and 6 of the spiro[4.5]decane skeleton, compounds (II) may exist in the form of at least one of the following stereoisomers: ##STR12##
The C(6)--OR.sup.1 bond can in fact possess a cis or trans configuration relative to the C(5)-O bond of the heterocycle. This fact may be visualized by means of formulae pairs (IIa) and (IIc), and (IIb) and (IId), respectively.
Moreover the methyl group at position 2 can also possess a cis or trans configuration relative to, for example, the C(5)-C(6) bond of the cyclohexane ring. This isomerism can be visualized by means of formulae pairs (IIa) and (IIb), and (IIc) and (IId)a, respectively.
All the above stereoisomers can be isolated in their pure state by means of a combination of several techniques such as fractional distillation, crystallisation and preparative vapour phase chromatography. A detailed description of the separation procedure applied to 2,6,10,10-tetramethyl-1-oxa-spiro[4.5]decan-6-ol and its corresponding acetate is given in Example 1.
For practical and economical reasons however, such a separation procedure is generally not necessary. Compounds (II) are most commonly used, in accordance with the present invention, as mixtures of "C(2)-epimers", i.e. as mixtures of stereoisomers (IIa) and (IIb) or stereoisomers (IIc) and (IId), respectively ##STR13## or even as mixtures comprising stereoisomers (IIa), (IIb), (IIc) and (IId).
Although it has been observed that in most of the applications the said mixtures and their individual constituents can develop analogous organoleptic effects, certain olfactive or gustative disparities have been observed.
Alcohol (IIA) for example (R.sup.1 =H in formula IIA) develops a particularly powerful woody and earthy odour whereas alcohol (IIB) possesses a more diffused woody note combined with a slightly flowery nuance. Ester derivatives, more precisely acetates (IIA) and (IIB) (R.sup.1 =acetyl in formulae IIA and IIB) also differ one from the other, (IIB) presenting a more developed flowery note.
When acetate (IIA) is used as flavouring ingredient, it can be characterized by its woody, amber-like and cedar-like taste, whereas acetate (IIB) develops a more diffused woody and slightly flowery taste, reminiscent in certain cases of that of ionones.
In accordance with one of the embodiments of the present invention, compounds (II) can be prepared starting from 1-(2,6,6-trimethyl-cyclohex-1-enyl)-butan-1,3-diol when R.sup.2 is a hydrogen atom or 1-(2,5,6,6-tetramethyl-cyclohex-1-enyl)-butan-1 3 diol when R.sup.2 is methyl (III) as illustrated hereinbelow: ##STR14##
The first step of the above process, which formally consists in the cyclisation of (III) and the concomitant elimination of a molecule of water, can be effected in the presence of an acidic reagent. The alkali metal salt of a polybasic acid such as sodium or potassium hydrogenosulfate can be conveniently used to this end, as well as a mineral or orgainc acid, e.g. sulfuric, phosphoric, hydrochloric or p-toluene-sulfonic acid. The said cyclisation can also be carried out in the presence of an acidic diatomaceous earth.
In accordance with a preferred embodiment of the above process, the said cyclisation can be effected by either
The epoxidation of compound (IV) can be effected by means of an organic peracid, in accordance with known techniques. Suitable peracids are performic, peracetic, trifluoroperacetic, perbenzoic, monochlorbenzoic or perphthalic acids.
The said epoxidation is moreover carried out in the presence of an organic solvent such as chloroform, methylene chloride, trichlorethylene or dichlorethane e.g. Peracetic acid in methylene chloride is preferably used, in the presence of a buffering agent such as sodium or potassium formate, acetate, propionate, butyrate, oxalate, citrate or tartrate e.g., sodium acetate being the preferred one.
Peracetic acid can also be prepared in situ from the action of hydrogen peroxide on acetic acid, in accordance with the method described in H.O. House, Modern Synthetic Reactions, 2nd ed. Benjamin Inc (1972), p. 293.
The reduction of compound (V) consists in the ring opening of the oxiran moiety of the molecule to give the corresponding tertiary alcohol (R.sup.1 =H in formula II). The said reduction can be performed in accordance with usual techniques, for example by means of an alkali metal aluminiumhydride such as lithiumaluminium hydride [see H.O. House, op.cit., p. 103].
The esterification in the thus obtained alcohol can be effected in accordance with the known techniques, for example by means of an acyl halide, preferably an acyl chloride, in the presence of an organic base such as N,N-dimethyl-aniline e.g.
2,6,10,10-Tetramethyl-1-oxa-spiro[4.5]dec-6-yl acetate was prepared as indicated hereinabove, from 2,6,10,10-tetramethyl-1-oxa-spiro[4.5]decan-6-ol and acetyl chloride. 2,6,10,10-Tetramethyl-1-oxa-spiro[4.5]dec-6-yl formate on the contrary was obtained by treating the above alcohol with formylimidazole, according to the method given in Liebigs Ann. Chem. 655, 95 (1962).
The diol of formula (III) used as starting material in the above process may be obtained for example in accordance with the method described in German Patent Application No. 2,315,640.
In accordance with another embodiment of the present invention, compounds (II) can be obtained from 2, 6, 10, 10-tetramethyl-1-oxa-spiro[4.5]deca-3,6-diene when R.sup.2 is a hydrogen atom and 2,6,9,10,10-pentamethyl-1-oxa-spiro[4.5]deca-3,6 diene when R.sup.2 is methyl (VI) as described in the following reaction scheme: ##STR15##
The epoxidation of compound (VI) is effected as described above for compound (IV).
The hydrogenation of both compounds (VII) and (VIII) is carried out in the presence of a metal catalyst, according to the usual techniques. The said hydrogenation may be effected in the presence of platinum oxide, palladium on charcoal or Raney-nickel e.g., and in the presence of an inert organic solvent such as an alcohol, methanol, ethanol or isopropanol e.g., or in the presence of an aliphatic or aromatic hydrocarbon such as hexane, benzene or toluene e.g. The said hydrogenation is preferably carried out by means of palladium on charcoal, in ethanol.
The reduction of compound (VII) is effected as mentioned above for compound (V), i.e. by means of an alkali metal aluminium hydride.
2,6,10,10-Tetramethyl-1-oxa-spiro[4.5]deca-3,6-diene or 2,6,9,10,10-pentamethyl-1-oxa-spiro[4.5]deca-3,6-diene used as starting materials in the above process may be obtained from an acetylenic derivative of formula ##STR16## by treating the said derivative with an acidic dehydrating agent, according to the process given in Swiss Pat. No. 544,733.
In accordance with a further embodiment of the present invention compounds (II) can also be prepared from an unsaturated alicyclic alcohol of formula ##STR17## by epoxidizing and subsequently subjecting to an acidic treatment said compound (IX) to give a spirane derivative of formula ##STR18## which is finally converted into compound (II) as mentioned hereinabove.
The epoxidation of 4-(2,6,6,-trimethyl-cyclohex-1-enyl)but-cis 3-ene-2-ol or 4-(2,5,6,6-tetramethyl-cyclohex-1-enyl)but-cis 3-ene-2-ol (IX) is effected as given above for compound (IV). According to a preferred embodiment of the above process, the said epoxidation is effected by means of peracetic acid in methylene chloride, in the presence of sodium acetate.
The acidic treatment of the product resulting from the epoxidation of compound (IX) may be carried out by means of a mineral or organic acid such as hydrochloric, sulfuric, phosphoric, benzenesulfonic or p-toluenesulfonic acid e.g., or an acidic diatomaceous earth.
The said acidic treatment is moreover effected in the presence of an inert organic solvent, preferably that of the preceding reaction step, methylene chloride in the present case.
Compound (IX) used as starting material in the above process may be obtained from .beta.-ionone, in accordance with the method given in J.Org.Chem. 38, 1247 (1973).